TWI756721B - Dim-to-warm led circuit - Google Patents

Abstract

Various embodiments include apparatuses and methods enabling a dim-to-warm circuit operation of an LED multi-colored array. In one example, an apparatus includes a hybrid driving-circuit coupled to the LED array and to a single control-device to receive an indication of a luminous flux desired from the LED array. A color temperature for the LED array is determined based on the desired luminous flux of the LED array. In various embodiments, the hybrid driving-circuit includes an analog current-division circuit to produce current for at least two LED current-driving sources and a multiplexer array coupled between the analog current-division circuit and the LED to provide periodically, for a predetermined amount of time, current from at least one of the at least two LED current-driving sources to at least two colors of the LED array. Other apparatuses and methods are described.

Description

Light-emitting diode circuit for dimming and toning

The subject matter disclosed herein pertains to color tuning of one or more light emitting diode arrays (LEDs) including lamps operating substantially in the visible portion of the electromagnetic spectrum. More specifically, the disclosed subject matter relates to a dimming tinting color tuning that enables a single color tuning device (eg, a dimmer) to control a color temperature in which a color temperature of an LED decreases as the LED is dimmed in intensity. equipment technology.

Light emitting diodes (LEDs) are commonly used in various lighting operations. The color appearance of an object is determined in part by the spectral power density (SPD) of the light illuminating the object. For a human viewing an object, SPD is the relative intensities of various wavelengths within the visible spectrum. However, other factors also affect color appearance. Furthermore, both a correlated color temperature (CCT) of the LED and a distance of the temperature of the LED from a black body line (BBL, also known as a black body locus or a Planckian locus) on the CCT may affect a human being. Perception of an object. In particular, such as in retail and hospitality lighting applications, there is a large market demand for LED lighting solutions in which the color temperature of one of the LEDs can be controlled. In particular, there is an increasing market demand for dimming and color-tuning lamps for home and office equipment. Contemporary lighting systems have addressed this dimming color LED market by using two control devices: one for light output (eg, luminous flux) and a separate device for CCT control. However, having two devices is expensive to install. It would be desirable to have the LED light change its color temperature relative to an amplitude of the incoming current when using only a single control device.

The information described in this section is provided to provide background to one of the subject matter disclosed below to those skilled in the art and should not be regarded as prior art with admission.

claim of priority

This application claims priority of US Patent Application No. 16/454,730 filed on June 27, 2019 and European Patent Application No. 19204908.8 filed on October 23, 2019, the entire contents of which are incorporated by reference manner is incorporated into this article. Cross-references to related applications

This application is related to commonly assigned US Patent Application Serial No. 16/844,923, filed April 9, 2020, entitled "DIM-TO-WARM LED CIRCUIT," which is incorporated by reference in its entirety.

The disclosed subject matter will now be described in detail with reference to several general and specific embodiments as illustrated in the various accompanying drawings. In the following description, numerous specific details are set forth in order to provide a thorough understanding of one of the disclosed subject matter. However, one skilled in the art will understand that the disclosed subject matter may be practiced without some or all of these specific details. In other instances, well-known procedural steps or structures have not been described in detail in order not to obscure the disclosed subject matter.

Examples of different light illumination systems and/or light emitting diode implementations will be described more fully below with reference to the accompanying drawings. These examples are not mutually exclusive, and features found in one example can be combined with features found in one or more other examples to achieve additional implementations. Accordingly, it will be understood that the examples shown in the accompanying drawings are provided for illustrative purposes only and that they are intended to limit the invention in any way. Throughout the text, the same numbers generally refer to the same elements.

It will be understood that although the terms first, second, third, etc. may be used herein to describe various elements. However, such elements should not be limited by these terms. These terms may be used to distinguish one element from another. For example, a first element could be termed a second element, and a second element could be termed a first element without departing from the scope of the disclosed subject matter. As used herein, the term "and/or" can include any and all combinations of one or more of the associated listed items.

It will also be understood that when an element is referred to as being "connected" or "coupled" to another element, it can be directly connected or coupled to the other element and/or connected or coupled to the other element through one or more intervening elements a component. In contrast, when an element is referred to as being "directly connected" or "directly coupled" to another element, there are no intervening elements between the element and the other element. It will be understood that these terms are intended to also encompass different orientations of the elements in addition to any orientation depicted in the figures.

Relative terms such as “below,” “above,” “upper,” “below,” “horizontal,” or “vertical” may be used herein to describe one element, region, or region as depicted in the figures relative to another A relationship between elements, regions, or regions. It will be understood that these terms are intended to also encompass different orientations of the device than the one depicted in the figures. Additionally, whether LEDs, LED arrays, electrical components, and/or electronic components are housed on one, two, or more electronic device boards may also depend on design constraints and/or a particular application.

Semiconductor-based light emitting devices or optical power emitting devices, such as devices that emit ultraviolet (UV) or infrared (IR) optical power, are among the most efficient light sources currently available. Such devices may include light emitting diodes, resonant cavity light emitting diodes, vertical cavity laser diodes, edge emitting lasers, or the like (referred to herein as LEDs). Due to their compact size and low power requirements, LEDs can be attractive candidates for many different applications. For example, they can be used as light sources (eg, flashlights and camera flashes) for handheld battery powered devices such as cameras and cellular phones. LEDs can also be used, for example, in automotive lighting, head-up display (HUD) lighting, horticultural lighting, street lighting, a flashlight for video, general lighting (eg, home, shop, office and studio lighting, theater/stage lighting) lighting and architectural lighting), augmented reality (AR) lighting, virtual reality (VR) lighting, backlighting as displays and IR spectroscopy. A single LED can provide less bright light than an incandescent light source, and thus multi-junction devices or LED arrays (such as monolithic LED arrays, micro LED arrays, etc.) can be used in applications where enhanced brightness is desired or required.

In a variety of environments where LED-based lamps (or related lighting devices) are used to illuminate objects and for general lighting, it may be desirable to control an LED-based lamp (or a single lamp with respect to a relative brightness (eg, luminous flux) of the lamp) ) one of the temperatures. For example, an end-user may desire that lights reduce the color temperature when they are dimmed. Such environments may include, for example, retail locations as well as hospitality locations, such as restaurants and the like. Another lamp metric other than CCT is the Color Rendering Index (CRI) of the lamp. CRI is defined by the International Commission on Illumination (CIE) and provides a quantitative measure of the ability of any light source, including LEDs, to accurately represent one of the colors in various objects compared to an ideal or natural light source. The highest possible CRI value is 100. Another quantitative lamp measure is _Duv . _Duv is a measure defined, for example, in CIE 1960 to express the distance of a color point from the BBL. The color point is a positive value if it is above the BBL, and a negative value if it is below the BBL. The color point above the BBL looks greenish and the color point below the BBL looks pinkish. The disclosed subject matter provides an apparatus for controlling a color temperature relative to a brightness level of a lamp. As described herein, color temperature is related to both CCT and _Duv in color tuning applications.

The disclosed subject matter relates to a method for driving LEDs of various colors (including, for example, primary color (red-green-blue or RGB) LEDs or desaturated (soft) RGB color LEDs) so that light of various color temperatures has a high color rendering index (CRI) and a high-efficiency hybrid drive scheme, specifically, using phosphor-converted color LEDs to solve color mixing.

The forward voltage of direct color LEDs decreases as the dominant wavelength increases. These LEDs can be driven using, for example, a multi-channel DC-to-DC converter. Advanced phosphor-converted color LEDs targeting high power efficiency and CRI have been developed, opening new possibilities for correlated color temperature (CCT) tuning applications. Some advanced color LEDs have desaturated color points and can be mixed to achieve whites with 90+ CRI over a wide CCT range. Other LEDs with 80+ CRI implementations or even 70+ CRI implementations can also be used with the disclosed subject matter. These possibilities use LED circuits that realize and increase or maximize this potential. At the same time, the control circuits described herein are compatible with single channel constant current drivers to facilitate market adoption.

As is known to those of ordinary skill, since the light output of an LED is proportional to the amount of current used to drive the LED, dimming of LEDs can be accomplished by, for example, reducing the forward current delivered to an LED. In addition to or in lieu of changing the amount of current used to drive each of the several individual LEDs, a controller box (described in detail below with reference to FIG. 6A ) can rapidly switch between "on" and "off" states Toggles the selection of LEDs to achieve an appropriate level of dimming and color temperature for the selected lamp.

In general, LED driver circuits are formed using an analog driver method or a pulse width modulation (PWM) driver method. In an analog driver, all colors are driven simultaneously. Each LED is driven independently by supplying a different current to each LED. Analog drivers cause a color shift and there is currently no way of shifting current in one of three ways. Analog driving typically results in some colors of the LED being driven in a low current mode and other times in a very high current mode. This wide dynamic range presents a challenge to sensing and control hardware.

In a PWM driver, the colors are turned on sequentially at high speed. Use the same current to drive each color. Controls the blending of colors by changing the time cycle of the action of each color. That is, one color can be driven twice as long as the other to add to the mix. Since human vision cannot perceive very rapidly changing colors, light appears to have a single color.

For example, a first LED is driven with a current for a predetermined amount of time, then the second LED is driven with the same current for a predetermined amount of time, and then the third LED is driven with a current for a predetermined amount of time. Each of the three predetermined amounts of time may be the same amount of time or a different amount of time. Therefore, the mixed colors are controlled by changing the time cycle of the action of each color. For example, if you have an RGB LED and desire a specific output, you can drive red for one part of the cycle, green for a different part of the cycle, and blue for another part of the cycle, based on human eye perception. Instead of driving the red LED at a lower current, it is driven at the same current for a shorter time. This example demonstrates the disadvantage of PWM, where LEDs are poorly utilized, thus resulting in an inefficient use of power.

Another advantage of the disclosed subject matter over the prior art is that the desaturated RGB approach can generate tunable light on or off the BBL while maintaining a high CRI. In contrast, various other prior art systems utilize a CCT approach in which the tunable color point falls on a line between the two primary colors of the LED (eg, R-G, R-B, or G-B).

1 shows an International Commission on Illumination (CIE) color including a black body line (BBL) 101 (also known as a Planck locus) that forms a basis for understanding various embodiments of the subject matter disclosed herein A portion of FIG. 100 . BBL 101 shows the chromaticity coordinates of a black body radiator of varying temperature. It is generally believed that in most lighting situations, the light source should have a chromaticity coordinate at or near the BBL 101 . The "closest" black body radiator is determined using various mathematical procedures known in the art. As mentioned above, this common lamp specification parameter is called Correlated Color Temperature (CCT). A useful and complementary way to further describe chromaticity is provided by the _{D uv} value, which is the chromaticity coordinate of a lamp above BBL 101 (a positive D _uv value) or below BBL 101 (a negative D uv value). _uv value) is an indicator of the extent.

Portions of the color map are shown to include several isotherms 117 . Even if each of these lines is not on BBL 101, any color point on isotherm 117 still has a constant CCT. For example, a first isotherm 117A has a CCT of 10,000K, a second isotherm 117B has a CCT of 5,000K, a third isotherm 117C has a CCT of 3,000K and a fourth isotherm The 117D has a CCT of 2,200K.

Continuing to refer to FIG. 1 , the CIE colormap 100 also shows ellipses, which are represented centered on the BBL 101 and extending over a distance from the BBL 101 by one step 105 , three steps 107 , five steps 109 , or seven One of the steps 111 is a Macadam ellipse (MAE) 103 . MAE is based on psychometric research and defines an area on the CIE chromaticity diagram that contains all the colors that a typical observer cannot distinguish from the color at the center of the ellipse. Thus, to a typical observer, each of MAE steps 105 to 111 (one step to seven steps) appears to be substantially the same color as the one at the center of each of MAE 103 . A series of curves 115A, 115B, 115C and 115D represent substantially equal distances from BBL 101 and are associated with Duv values such as +0.006, _+0.003 , 0, -0.003 and -0.006, respectively.

Referring now to FIG. 2A and with continued reference to FIG. 1 , FIG. 2A shows a chromaticity diagram 200 having a red (R) LED at coordinates 205 , a green (G) LED at coordinates 201 , and one at coordinates 203 The approximate chromaticity coordinates of the color of the typical coordinates of the blue (B) LED (as noted on the xy scale of the chromaticity diagram 200). 2A shows an example of a chromaticity diagram 200 for defining the wavelength spectrum of a visible light source, according to some embodiments. The chromaticity diagram 200 of FIG. 2A is only one way of defining a wavelength spectrum of a visible light source; other suitable definitions are known in the art and may also be used with various embodiments of the disclosed subject matter described herein use.

A convenient way to specify a portion of the chromaticity diagram 200 is through a set of equations in the x-y plane, where each equation has a locus of the solution that defines a line on the chromaticity diagram 200 . Lines may intersect to designate a particular area, as described in more detail below with reference to Figure 2B. As an alternative definition, a white light source may emit light corresponding to light from a blackbody source operating at a given color temperature.

Chromaticity diagram 200 also shows BBL 101 as described above with reference to FIG. 1 . Each of the three LED coordinate positions 201, 203, 205 is the CCT coordinate of the "fully saturated" LEDs of the respective colors green, blue and red. However, if a "white light" is produced by combining a certain ratio of R, G, and B LEDs, the CRI for this combination will be extremely low. Typically, in the environments described above, such as retail or hospitality environments, a CRI of about 90 or higher may be expected.

Figure 2B shows a revised version of the chromaticity diagram 200 of Figure 2A. However, the chromaticity diagram 250 of FIG. 2B shows the approximate chromaticity coordinates of the desaturated (soft) R, G, and B LEDs close to BBL 101 . Display the coordinate values of a desaturated red (R) LED at coordinate 255, a desaturated green (G) LED at coordinate 253, and a desaturated blue (B) LED at coordinate 251 (as shown in chromaticity diagram 250). noted on the xy scale). In various embodiments, a color temperature range for the desaturated R, G, and B LEDs may be in a range from about 1800K to about 2500K. In other embodiments, the desaturated R, G, and B LEDs may be in a color temperature range of about 2700K to about 6500K. As mentioned above, the color rendering index (CRI) of a light source does not indicate the apparent color of the light source; this information is given by the correlated color temperature (CCT). Thus, CRI is a quantitative measure of the ability of a light source to faithfully represent the color of various objects compared to an ideal or natural light source.

In a particular exemplary embodiment, a triangle 257 formed between each of the coordinate values of the desaturated R, G, and B LEDs is also shown. Desaturated R, G, and B LEDs are formed (eg, by a mixture of phosphors and/or a mixture of materials used to form LEDs as known in the art) to have coordinate values close to BBL 101 . Thus, the coordinate positions of the respective desaturated R, G, and B LEDs, and as outlined by triangle 257, have a CRI of about 90 or greater. Thus, the choice of a correlated color temperature (CCT) can be selected in the color tuning applications described herein such that all combinations of the selected CCTs all result in lamps having a CRI of 90 or greater. Each of the desaturated R, G, and B LEDs may include a single LED or an array (or group) of LEDs, where each LED within the array or group has one of the same or similar ones as the other LEDs within the array or group Desaturate colors. A combination of one or more desaturated R, G, and B LEDs includes a lamp.

FIG. 3 shows a prior art color tuning device 300 that requires a single flux control device 301 and a single CCT control device 303 . The flux control device 301 is coupled to a single channel driver circuit 305 and the CCT control device is coupled to a combined LED driver circuit/LED array 320 . The combined LED driver circuit/LED array 320 can be a current driver circuit, a PWM driver circuit, or a mixed current driver/PWM driver circuit. Each of the flux control device 301, CCT control device 303, and single channel driver circuit 305 are located in a customer facility 310 and all must be installed in accordance with applicable national and local regulations governing high voltage circuits. The combined LED driver circuit/LED array 320 is typically located remotely from the customer facility 310 . Therefore, both the initial purchase price and the installation price can be large.

4 shows an illustrative embodiment of a color tuning device 400 using a single control device 401 in accordance with various embodiments of the disclosed subject matter. A single control device 401 is coupled to a single channel driver circuit 403 , both of which are within a customer installation area 410 . Single channel driver circuit 403 is coupled to a combined hybrid driver circuit/desaturated LED array 420 . The combined hybrid driver circuit/desaturated LED array 420 is typically located remotely from the customer installation area 410 (but typically still within a customer facility). One embodiment of a combined hybrid drive circuit/desaturated LED array 420 is described in detail below with reference to FIGS. 6A and 6B . To a considerable extent, color tuning device 400 requires only a single device to control both luminous flux (and luminous intensity) and color temperature as described in more detail below with reference to FIG. 5 .

In various embodiments, the single control device 401 is a variable resistance device such as, for example, a slider-type dimmer (a linear operating device) or a rotary-type dimmer. In various embodiments, the single control device 401 includes a voltage divider. A single control device 401 provides a continuously variable output voltage or a set of discrete output voltages. In an embodiment, the single control device 401 may already be used by the end user in the customer installation area 410 .

5 shows an example of a graph 500 indicating color temperature 501 as a function of luminous flux 503 in accordance with various embodiments of the disclosed subject matter. A curve 505 of graph 500 indicates that as luminous flux 503 increases, a resulting color temperature 501 also increases monotonically with flux. Thus, the color temperature of an LED array (see Figure 6A) increases as an end user of the system (eg, see Figure 4) increases the "brightness" (luminous flux) of the array. Conversely, the color temperature of the LED array decreases as the end user "dimming" the LED array. Accordingly, various embodiments of the disclosed subject matter describe a dimming and toning LED circuit. The dimming and tinting LED circuit is also used to simulate the dimming and tinting behavior of a standard incandescent light bulb - as an end user dims the incandescent light bulb, the light bulb's color temperature drops proportionally.

FIG. 6A shows an exemplary embodiment of a hybrid drive circuit 600 for RGB tuning. Hybrid driver circuit 600 includes an LED driver 601 electrically coupled to a voltage regulator 603 . The LED driver 601 and the voltage regulator 603 together generate a regulated current I ₀ and a voltage V _LED . Hybrid driver circuit 600 is also shown to include a type of split shunt circuit 610A, a multiplexer array 620, and an LED multicolor array 630.

LED multi-color array 630 may include one or any number of LED arrays 631 of a first color, one or any number of LED arrays 633 of a second color, and one or any number of LED arrays 635 of a third color. In various embodiments, more than three colors may be used. Also, LED arrays 631, 633, 635 may include only a single LED in each array.

The LED arrays 631, 633, 635 can be designed to be tuned using the hybrid drive circuit 600 as described in detail herein. In one embodiment of the hybrid driver circuit 600, the first color LED array 631 includes green LEDs, the second color LED array 633 includes red LEDs and the third color LED array 635 includes blue LEDs. However, any color group may be selected for the LED arrays 631 , 633 , 635 . For example, each of the LED arrays 631, 633, 635 may include desaturated green LEDs, desaturated red LEDs, and desaturated blue LEDs, respectively, as described above with reference to Figure 2B. As can be appreciated by those of ordinary skill, assigning a color to a particular channel is only one design choice, and while many other designs are contemplated, the current description uses the color combinations just discussed above to provide only one of the hybrid driver circuits 600 described herein better understanding.

The hybrid drive circuit 600 includes an analog shunt circuit 610A configured to divide the incoming current _IO into two currents _IL and IR respectively as a first branch line _619L (one of the analog shunt circuits 610A). The output on the left current branch 616L) and a second branch line _619R (analogous to the right current branch _616R of the shunt circuit 610A) using various resistors as shown (eg R1, R2, _R3 , _RSl , R _S2 , R _UPPER , and R _LOWER ) and a connection between V _DD and ground. In an embodiment, the analog shunt circuit 610A may take the form of a drive circuit to provide each of the two branch lines 619L, 619R with equal currents. In an embodiment, the analog shunt circuit 610A may take the form of a drive circuit to provide each of the two branch lines 619L, 619R with unequal currents.

The analog shunt circuit 610A can further account for any mismatch in forward voltage between LEDs of different colors, while allowing precise control of the drive current in each color. Alternatively, analog shunt circuit 610A may allow one of the deliberately unequal divisions of the currents, which cannot be accomplished by simply switching on various combinations of LED arrays 631, 633, 635 (switching of circuits is described in more detail below with reference to multiplexer array 620). part) to complete. As can be appreciated by those of ordinary skill, other analog shunt circuits may be utilized without departing from the scope of the disclosed subject matter. A shunt circuit 610A like that described herein is provided as one example of a shunt circuit so that those skilled in the art will more fully appreciate the disclosed subject matter.

Additionally, the analog shunt circuit 610A may be mounted on, for example, a printed circuit board (PCB) to operate using the LED driver 601 and the LED multicolor array 630 . LED driver 601 may be a conventional LED driver such as one known in the art. Thus, analog shunt circuit 610A may allow LED driver 601 to be used in applications that utilize two or more of LED multicolor array 630 . In other embodiments, the analog shunt circuit 610A is mounted, for example, on a PCB separate from at least one of the LED driver 601 and the LED multicolor array 630 .

Each current branch of analog shunt circuit 610A may include a sense resistor (eg, R _S1 and R _S2 ). For example, in an embodiment having one of the two current paths as shown in FIG. 6A, the analog shunt circuit 610A includes a first sense resistor _615L ( R _S1 ) and a second sense resistor 615R (R _S2 ) for sensing a second voltage V _{SENSE_R2} of the right current branch 616R. The voltage at V _{SENSE_R1 results} from the current flowing through the first sense resistor 615L (R _S1 ) and the voltage at V _{SENSE_R2 results} from the current flowing through the second sense resistor 615R (R _S2 ).

A shunt circuit 610A like FIG. 6A is also shown as including an arithmetic device 610B. However, in some embodiments, computing device 610B may be used in conjunction with or replaced by a microcontroller, as discussed below with reference to FIG. 6B. The computing device 610B is configured to compare the first sensed voltage V _{SENSE_R1} with the second sensed voltage V _{SENSE_R2} to determine a set voltage V _SET . If the first sensed voltage V _{SENSE_R1} is lower than the second sensed voltage V _{SENSE_R2} , the computing device 610B is configured to increase the set voltage V _SET . If the first sensed voltage V _{SENSE_R1} is greater than the second sensed voltage V _{SENSE_R2} , the computing device 610B is configured to lower the set voltage V _SET .

In a particular illustrative embodiment, computing device 610B includes an operational amplifier 612, a capacitor 614 between a location on which the set voltage _VSET is carried and ground, and a lower resistor R placed in parallel with capacitor 614 _LOWER (used as one of the discharge resistors for capacitor 614). Additionally, an upper resistor R _UPPER is placed in series with both resistor R _LOWER and capacitor 614 . The benefits of the upper resistor _RUPPER are discussed below.

The first sensed voltage V _{SENSE_R1} and the second sensed voltage V _{SENSE_R2 are} fed to an operational amplifier 612 . The computing device 610B may be configured to compare the first sensed voltage V _{SENSE_R1} with the second sensed voltage V _{SENSE_R2} by subtracting the first sensed voltage V _{SENSE_R1} from the second sensed voltage V _{SENSE_R2} . When the operational amplifier 612 is in regulation, the computing device 610B may be configured to convert the difference between the first sensed voltage V _{SENSE_R1} and the second sensed voltage V _{SENSE_R2} into a charging current. The charging current is used to charge the capacitor 614 when the first sensed voltage V _{SENSE_R1} is less than the second sensed voltage V _{SENSE_R2} , thereby increasing the set voltage V _SET . The computing device 610B may be configured to convert the difference between the first sensed voltage V _{SENSE_R1} and the second sensed voltage V _{SENSE_R2} into a discharge resistor R _LOWER . When the first sensed voltage V _{SENSE_R1} is greater than the second sensed voltage V _{SENSE_R2} , the discharge resistor R _LOWER reduces the set voltage V _SET .

Therefore, if the first sensed voltage V _{SENSE_R1 is} higher than the second sensed voltage V _{SENSE_R2} , the computing device 610B may lower the set voltage V _SET , which in turn lowers the first gate voltage supplying power to the left current branch 616L V _GATE1 . Therefore, when the operational amplifier 612 is in regulation, the first sensed voltage V _{SENSE_R1} is approximately equal to the second sensed voltage V _{SENSE_R2} . Thus, during steady state, the ratio of the current of the left current branch 616L to the current of the right current branch 616R is equal to the value of the second sense resistor 615R (R _S2 ) to the value of the first sense resistor 615L (R _S1 ) ratio.

Therefore, when the value of the first sense resistor 615L (R _S1 ) is equal to the value of the second sense resistor 615R (R _S2 ), the current flowing through the first sense resistor 615L (R _S1 ) is equal to the current flowing through the first sense resistor 615L (R S1 ) The current of the second sense resistor 615R (R _S2 ), the hybrid drive current 600 divides the current into two equal parts (assuming that the current drawn by the auxiliary circuit (such as that generated by the supply voltage) is negligible). It should be noted that, as those of ordinary skill will appreciate and as discussed above, the computing device 610B shown in FIG. 6A is only one of many possible embodiments.

With continued reference to FIG. 6A, in various embodiments, the set voltage V _SET is provided to a voltage controlled current source. The voltage controlled current source can be implemented using an additional operational amplifier 611 . The additional operational amplifier 611 then provides a first gate voltage V _GATE1 . The first gate voltage V _GATE1 is provided to an input of a first transistor 613L, which provides a drive current source IL on the first branch line _619L . The first transistor 613L may be, for example, a conventional metal oxide semiconductor field effect transistor (MOSFET). In a specific exemplary embodiment, the first transistor 613L may be an n-channel MOSFET. As can be appreciated by those skilled in the art, the first transistor 613L may be any type of switching device known in the art.

Continuing with this embodiment, a second transistor 613R provides a drive current source IR on the second branch line _619R . Like the first transistor 613L, the second transistor 613R may also comprise a conventional MOSFET or related device type. In a specific exemplary embodiment, the second transistor 613R is an n-channel MOSFET. The second transistor 613R may only be turned on when the left current branch 616L is in regulation. A second gate voltage V _GATE2 allows current to flow through the second transistor 613R.

The second gate voltage V _GATE2 may be fed to a reference (REF) input of a shunt regulator 617 . For example, in an exemplary embodiment, the shunt regulator 617 has an internal reference voltage of 2.5V. The shunt regulator 617 is configured to sink a large current when the voltage applied at the REF node of the shunt regulator 617 is greater than 2.5 V. The shunt regulator 617 may draw a small quiescent current when the voltage applied at the REF node of the shunt regulator 617 is less than or equal to about 2.5 V. Shunt regulator 617 may include a Zener diode, as known to those of ordinary skill.

The large sink current pulls down the gate voltage of the second transistor 613R to a level below its threshold voltage, which can turn off the second transistor 613R. In some cases, the shunt regulator 617 may not be able to pull the cathode more than the forward voltage _Vf of one of the diodes below the REF node. Therefore, the second transistor 613R may have a threshold voltage higher than 2.5V. Alternatively, a shunt regulator with a lower internal reference voltage (such as, for example, 1.24 V) can be used. Benefits of Resistor R _UPPER

As described above and with continued reference to computing device 610B shown in FIG. 6A , upper resistor R _UPPER is placed in series with both resistor R _LOWER and capacitor 614 . In general, the computing device 610B (or the microcontroller described below with reference to FIG. 6B ) reacts to a 0 V to 10 V analog signal and changes the R/G/B colors of the LED arrays 631, 633, 635 according to an algorithm ratio. In order for the light to change color with the input current, the current needs to be sensed and the signal needs to be rerouted to the 0 V to 10 V input.

In prior art hybrid drive circuits, the V _{SENSE_R1} signal is fed to a microcontroller or other type of computing device. However, without resistor R _UPPER , there is one between the input dynamic range of an internal analog-to-digital converter (ADC) and the power consumption in sense resistors R _S1 and R _S2 in the prior art circuit trade off.

Resistor R _UPPER as shown in the hybrid drive circuit 600 of FIG. 6A includes the above-mentioned trade-off between improved dynamic range and power consumption of the sense resistor. Resistor R _UPPER is inserted between the source terminal of the MOSFET coupled to V _SET and resistor R _LOWER in parallel with capacitor 614 . One of the two resistors R _UPPER and R _LOWER is combined to form a resistive voltage divider. One of the original functions of this circuit is to ensure that the quantities _VSET equal to V _{SENSE_R1} and V _{SENSE_R2} are still met under equilibrium. However, an additional benefit of adding resistor R _UPPER is that the voltage at V _{SENSE_AMPLIFIED} is now an amplified version of the voltage at V _SET . Amplification greatly improves the input signal range of the ADC without increasing power consumption in sense resistors R _S1 and R _S2 .

因此，放大因數係：

For example, the amplification of V _SET takes the form:

Therefore, the magnification factor is:

In a particular exemplary embodiment, the target peak current is assumed to be 1 ampere (A). R _S1 and R _S2 may be chosen to be 0.47 ohms (Ω) each, thus giving a peak voltage of 0.47 V. (This is because I x R = V, in this example, 1 A x 0.47 Ω = 0.47 V). To double this voltage, the value of R _UPPER can be chosen to be, for example, 3.3 kΩ, and R _LOWER can be chosen to be, for example, 2.2 kΩ. Therefore, the amplification factor is (1 + 3.3 kΩ/2.2 kΩ) = 2.5. Therefore, in this example, the value of V _{SENSE_AMPLIFIED} = 2.5 ^. (V _SET ).

These values are provided as examples only so that the disclosed subject matter will therefore be more fully appreciated by those of ordinary skill after reading and understanding the information provided herein. Various other values may be chosen depending on the specific parameters and expectations of a given circuit.

With continued reference to FIG. 6A, the hybrid drive circuit 600 includes a configuration to electrically couple two of the three LED arrays 631, 633, 635 to the first branch line 619L and the second branch line 619R, thereby providing the generation by the analog shunt circuit 610A The multiplexer array 620 of the two current sources _IL and IR _. In an exemplary embodiment, the multiplexer array 620 includes a plurality of switching devices 621 (S ₁ ), 623 (S ₂ ), 625 (S ₃ ), 627 (S ₄ ). Although four switching devices are shown, multiplexer array 620 may include more or fewer switches. In a particular exemplary embodiment, the switching devices 621, 623, 625, 627 comprise MOSFET transistors or similar types of switching devices known in the art. Multiplexer array 620 is configured to conduct currents _IL and IR into two colors of LED multicolor array 630 substantially simultaneously _.

Operationally, the hybrid drive circuit 600 for RGB tuning uses an analog shunt circuit 610A to drive two colors of the three LED arrays 631, 633, 635 substantially simultaneously. The hybrid drive circuit 600 then time-divides the PWM with the third (remaining) color overlay of the three LED arrays 631, 633, 635.

When two colors are driven simultaneously, a virtual color point is produced. The _ratio between the currents _IL and IR may be predetermined. For example, the ratio between the currents can be 1:1 or slightly different to maximize efficiency. However, any ratio can be used. Where three colors of three LED arrays 631, 633, 635 are used, three virtual color points (RG, RB, GB) can be generated using desaturated RGB LEDs such as those described herein. The triangle created by the three virtual color points (RG, RB, GB) defines the color gamut of the hybrid drive objects disclosed herein. In various exemplary embodiments, one or more primary colors R/G/B (a fourth or higher color point) may be included for mixing.

Referring now to FIG. 6B, a microcontroller 650 may be used in conjunction with or in place of computing device 610B. For example, the microcontroller 650 can perform complex signal processing using potentially less PCB resources than the analogous circuit described above. Those skilled in the art will recognize that other types of devices may operate the same or similar to microcontroller 650 . Several such devices are described below.

In this particular embodiment, the microcontroller 650 receives the input signal and can perform the operations (operations of S1 and S4) of the switching devices 621, 627 (the first switch and the fourth switch) of FIG. 6A. In an embodiment, microcontroller 650 is configured to monitor the absolute value of the input current by sensing V _{SENSE_R1} at a sense voltage input 651 and, for example, a temperature of a plate on which microcontroller 650 is positioned. The temperature is sensed using, for example, a negative temperature coefficient (NTC) resistor (thermistor, not shown) coupled to an NTC input 655 of the microcontroller 650 . These two readings V _{SENSE_R1} at sense voltage input 651 and NTC input 655 can be used to compensate for a potential color shift in one of the LED arrays 631 , 633 , 635 due to drive current and temperature. The 0 V to 10 V input can be used as a control input 653. As described herein, microcontroller 650 may be mapped to a CCT tuning curve. Microcontroller 650 translates incoming commands (eg, color temperature as a function of luminous flux, see FIG. 5 ) into operation of multiplexer array 620 . Specifically, the microcontroller 650 may provide a first output signal _IL at a first output 657 to control switch S1 and a second output signal IR at a second output ₆₅₉ to control switch S4.

As described above, the input current is sensed through sense resistor R _S1 and converted to a voltage V _{SENSE_R1} . An amplified version of one of the voltages V _{SENSE_AMPLIFIED} is fed to arithmetic device 610B (see Figure 6A) or to microcontroller 650 (see Figure 6B). The microcontroller 650 stores a digitized CCT versus current curve. The digital CCT versus current curve can be created in various ways known to those skilled in the art and stored in software (eg, within microcontroller 650), firmware (eg, an EEPROM), or hardware (eg, a field programmable gate) array (FPGA)). The instructions may then select a CCT corresponding to the sensed current level. In its simplest form, the maximum current can be hard-coded in microcontroller 650 and associated with a maximum color temperature (eg, 3500K).

In various embodiments, computing device 610B and/or microcontroller 650 may be configured to automatically adjust CCT versus current curve 500 of FIG. 5 by having, for example, a special calibration mode. For example, if the microcontroller 650 is power cycled in a special sequence (eg, a combination of long and short power up/down cycles), it can enter a calibration mode. When in this calibration mode, the user (eg, a calibration technician at the factory or an advanced end user) is required to vary the driver output current between the minimum and maximum levels of the driver output. The microcontroller 650 then stores these two values in an internal memory (to the microcontroller 650 or to a board on which the microcontroller 650 is located), eg, as described above. Internal memory may take several forms including, for example, Electrically Erasable Programmable Read Only Memory (EEPROM), Phase Change Memory (PCM), Flash Memory, or various other types of non-volatile memory known in the art. Volatile memory device.

Referring now to FIG. 7, an example of a method 700 for providing a dimming toning operation of an LED light source in accordance with various exemplary embodiments of the disclosed subject matter is shown. Method 700 describes dimming and toning operations for LED multi-color array 630 using, for example, the hybrid drive circuit of FIG. 6A. The exemplary operations shown enable combining multiple LED multi-color arrays 630 to produce a desired color temperature for a given light-signal level from a single control device of FIG. 4 . The received light-signal level is read by a single channel driver circuit 403 (eg, which may include the LED driver 601 of Figure 6A). The glow-signal levels can then be used to calibrate, for example, computing device 610B and/or microcontroller 650 as described above.

Continuing to refer to FIG. 7, at operation 701, method 700 divides an input current into a first current _IL and a second current IR via a type of shunt circuit _. At operation 703, a first current is provided to a first of the three colors of the LED multi-color array 630 and a second current is provided to the LEDs substantially simultaneously via the multiplexer array 620 during a first portion of a period The second of the three colors of the multicolor array 630 . At operation 705, a first current is provided to a second of the three colors of the LED multi-color array 630 and a second current is provided to the LEDs substantially simultaneously via the multiplexer array 620 during a second portion of the period One of the three colors of the multicolor array 630 is the third. At operation 707, a first current is provided to a first of the three colors of the LED multi-color array 630 and a second current is provided to the LED multi-color via the multiplexer array substantially simultaneously during a third portion of the period. The third of the three colors of the color array 630 .

In method 700 , the provision of the first current and the second current to different pairs of electrons of the LED multi-color array 630 may use a pulse for supplying a drive current to a third of the three colors of the LED multi-color array 630 A wide modulation (PWM) time truncation occurs. In various embodiments, the PWM may be substantially equal between the combination of the first of the three colors of the LEDs, the second of the three colors of the LEDs, and the third of the three colors of the LEDs. In various embodiments, the PWM may be different depending on the desired driving characteristics of the LEDs.

After reading and understanding the disclosed subject matter, one of ordinary skill will recognize that the method can be applied to conventional RGB colors of LEDs or desaturated RGB colors of LEDs. Those skilled in the art will also recognize that additional or fewer colors of LEDs can be used.

In various embodiments, many of the components may include one or more modules configured to implement the functions disclosed herein. In some embodiments, a module may constitute a software module (eg, code stored on or otherwise embodied in a machine-readable medium or a transmission medium), a hardware module body modules or any suitable combination thereof. A "hardware module" is a tangible (eg, non-transitory) physical component (eg, a set of one or more microprocessors or other hardware-based devices) capable of performing certain operations and interpreting certain signals. One or more modules may be configured or configured in a specific physical manner. In various embodiments, one or more microprocessors, or one or more hardware modules thereof, may be configured by software (eg, an application program or portion thereof) to operate to perform the functions directed to the module herein. Describes the operation of a hardware module.

In some exemplary embodiments, a hardware module may be implemented, for example, mechanically or electronically, or by any suitable combination thereof. For example, a hardware module may contain dedicated circuitry or logic that is permanently configured to perform a particular operation. A hardware module can be or include a dedicated processor, such as a Field Programmable Gate Array (FPGA) or an Application Specific Integrated Circuit (ASIC). A hardware module may also include programmable logic or circuitry that is temporarily configured by software to perform specific operations, such as the interpretation of various states and transitions within a finite state machine. As an example, a hardware module may include software contained within a CPU or another programmable processor. It will be appreciated that the decision to mechanically and electrically implement a hardware module as a dedicated and permanently configured circuit or as a temporarily configured circuit (eg, by software configuration) can be driven by cost and time considerations.

The foregoing description includes illustrative examples, devices, systems, and methods that embody the disclosed subject matter. In the description, for the purposes of explanation, numerous specific details are set forth to provide an understanding of one of the embodiments of the disclosed subject matter. However, it will be apparent to those of ordinary skill that embodiments of the subject matter may be practiced without these specific details. Furthermore, well-known structures, materials and techniques have not been shown in detail in order not to obscure the various depicted embodiments.

As used herein, the term "or" can be interpreted in an inclusive or exclusive sense. Furthermore, other embodiments will be appreciated by those of ordinary skill after reading and understanding the disclosure provided. Furthermore, after reading and understanding the disclosure provided herein, those of ordinary skill will readily appreciate that the various combinations of techniques and examples provided herein can all be applied in various combinations.

Although each embodiment is discussed separately, these separate embodiments are not intended to be considered separate technologies or designs. As indicated above, each of the various parts may be associated with each other, and each may be used separately or in combination with other types of electrical control devices, such as dimmers and related devices. Thus, although various embodiments of methods, operations, and procedures have been described, these methods, operations, and procedures may be used separately or in various combinations.

Accordingly, many modifications and variations are possible, as will be apparent to those of ordinary skill after reading and understanding the disclosure provided herein. In addition to the methods and apparatuses enumerated herein, those skilled in the art will also appreciate from the foregoing description functionally equivalent methods and apparatuses that are within the scope of the present invention. Portions and features of some embodiments may be included in or substituted for those of other embodiments. Such modifications and variations are intended to fall within one of the scope of the appended invention claims. Accordingly, the present invention should be limited only by the terms of the appended claims, along with the full scope of equivalents to which such claims are entitled. It is also to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting.

This Abstract is provided to allow the reader to quickly ascertain the nature of the technical disclosure. The Abstract is presented with the understanding that it will not be used to interpret or limit the scope of the invention claimed. In addition, in the foregoing [Embodiment], it can be seen that various features may be grouped into a single embodiment for the purpose of simplifying the invention. This method of the present invention should not be construed as limiting the scope of the invention claimed. Therefore, the following invention claims are hereby incorporated into the [Embodiment], wherein each technical solution is independently regarded as a separate embodiment.

100: International Commission on Illumination (CIE) Color Chart 101: Black Body Line (BBL) 103: MacAdam Ellipse (MAE) 105: MacAdam Ellipse (MAE) Step Size 107: MacAdam Ellipse (MAE) Step Size 109: MacAdam Ellipse (MAE) Step 111: MacAdam Ellipse (MAE) Step 115A: Curve 115B: Curve 115C: Curve 115D: Curve 117: Isotherm 117A: First Isotherm 117B: Second Isotherm 117C: Third Isotherm 117D: Fourth Isotherm 200: Chromaticity Diagram 201: Coordinate/Light Emitting Diode (LED) Coordinate Position 203: Coordinate/Light Emitting Diode (LED) Coordinate Position 205: Coordinate/Light Emitting Diode (LED) LED) coordinate position 250: chromaticity diagram 251: coordinate 253: coordinate 255: coordinate 257: triangle 300: color tuning device 301: flux control device 303: correlated color temperature (CCT) control device 305: single channel driver circuit 310: customer Facility 320: Combined Light Emitting Diode (LED) Driver Circuit/Light Emitting Diode (LED) Array 400: Color Tuning Unit 401: Single Control Unit 403: Single Channel Driver Circuit 410: Customer Mounting Area 420: Combined Hybrid Driver Circuit/ Desaturated Light Emitting Diode (LED) Array 500: Graph/Correlated Color Temperature (CCT) vs Current Curve 501: Color Temperature 503: Luminous Flux 505: Curve 600: Hybrid Drive Circuit 601: Light Emitting Diode (LED) Driver 603: Voltage Regulation device 610A: analog shunt circuit 610B: arithmetic device 611: additional operational amplifier 612: operational amplifier 613L: first transistor 613R: second transistor 614: capacitor 615L: first sense resistor 615R: second sense resistor 616L: Left Current Branch 616R: Right Current Branch 617: Shunt Regulator 619L: First Branch 619R: Second Branch 620: Multiplexer Array 621: Switch 623: Switch 625: Switch 627: Switch 630: Light Emitting Diode (LED) Multicolor Array 631: Light Emitting Diode (LED) Array 633: Light Emitting Diode (LED) Array 635: Light Emitting Diode (LED) Array 650: Microcontroller 651: Sensing Voltage measurement input 653: Control input 655: Negative temperature coefficient (NTC) input 657: First output 659: Second output 700: Method 701: Operation 703: Operation 705: Operation 707: Operation I ₀ : Steady current _IL : Current /drive current source I _R : current / drive current source R _LOWER : lower resistor/discharge resistor R _UPPER : upper resistor R _S1 : sense resistor R _S2 : sense resistor V _GATE1 : first gate voltage V _GATE2 : The second gate voltage V _{SENSE_AMPLIFIE D} : voltage V _{SENSE_R1} : first voltage/first sensed voltage V _{SENSE_R2} : second voltage/second sensed voltage V _SET : set voltage

Figure 1 shows a portion of a Commission International Illumination (CIE) color map including a black body line (BBL);

2A shows a chromaticity diagram with approximate chromaticity coordinates for the colors of typical red (R), green (G), and blue (B) LEDs on the graph and including a BBL;

2B shows a revised version of the chromaticity diagram of FIG. 2A with approximate chromaticity coordinates of desaturated R, G, and B LEDs near BBL, according to various embodiments of the disclosed subject matter;

3 shows a prior art color tuning device requiring a single flux control device and a single CCT control device;

4 shows an illustrative embodiment of a color tuning device using a single control device in accordance with various embodiments of the disclosed subject matter;

5 shows an example of a graph indicating color temperature as a function of luminous flux according to various embodiments of the disclosed subject matter;

6A shows an exemplary embodiment of a color tuning circuit in accordance with various exemplary embodiments of the disclosed subject matter;

Figure 6B shows an exemplary embodiment of a microcontroller that can be used with the color tuning circuit of Figure 6A; and

7 shows an example of a method of providing a dimming toning operation of an LED light source in accordance with various illustrative embodiments of the disclosed subject matter.

400: Color Tuning Device

401: Single control device

403: Single channel driver circuit

410: Customer Installation Area

420: Combined Hybrid Drive Circuit/Desaturated Light Emitting Diode (LED) Array

Claims (20)

A dimming and toning circuit device, comprising: a hybrid drive circuit coupled to a light emitting diode (LED) multicolor array and coupled to a single control device, the hybrid drive circuit for receiving from the single control device An indication of a light-emitting signal level and adjusting a color temperature and a corresponding luminous flux of the LED multicolor array based on the received light-emitting signal level, the hybrid driving circuit includes: a type of shunt circuit for generating the current of at least two LED current drive sources, the analog shunt circuit further comprising a resistive divider circuit configured to generate an amplified voltage signal; and a multiplexer array coupled to the Between the analog shunt circuit and the LED multicolor array, the multiplexer array is configured to periodically provide current from at least one of the at least two LED current drive sources to at least two of the LED multicolor array The time for the color to reach a predetermined amount. The dimming and coloring circuit apparatus of claim 1, further comprising an LED driver electrically coupled to a voltage regulator, the voltage regulator configured to provide a voltage signal for the LED multi-color array, the LED driver and A combination of the voltage regulators is used to provide a regulated current as an input to the analog shunt circuit. The dimming and color grading circuit device of claim 1, wherein the colors of the LEDs in the LED multi-color array include at least one red LED, at least one green LED and at least one blue LED. The dimming and toning circuit device of claim 1, wherein the LED multi-color array comprises at least one desaturated red LED, at least one desaturated green LED, and at least one desaturated blue LED. The dimming and toning circuit device of claim 1, wherein the multiplexer array includes at least four switching devices. The dimming toning circuit apparatus of claim 1, wherein each of the at least two LED current drive sources is configured to supply equal amounts of current to the LED multicolor array. The dimming toning circuit apparatus of claim 1, wherein each of the at least two LED current drive sources is configured to supply unequal amounts of current to the LED multicolor array. The dimming toning circuit apparatus of claim 1, further comprising a voltage controlled current source configured to supply current to the analog shunt circuit to generate current for the at least two LEDs The current of the drive source. The dimming and toning circuit apparatus of claim 8, further comprising an arithmetic device configured to compare a first sensed voltage V _{SENSE_R1} and a second sensed voltage V _{SENSE_R2} to determine and supply A set voltage V _SET , which is an input voltage of the voltage-controlled current source. The dimming and toning circuit device of claim 9, wherein the amplified voltage signal V _{SENSE_AMPLIFIED} is an amplified version of the set voltage V _SET . The dimming toning circuit apparatus of claim 1, wherein the hybrid drive circuit is further configured to supply a pulse width modulated (PWM) time dicing signal to selected ones of the LED multicolor array. The dimming and toning circuit apparatus of claim 1, further comprising a microcontroller for mapping the received lighting signal level from the single control device to a correlated color temperature (CCT) to provide An input for setting the color temperature of the LED multicolor array. The dimming and toning circuit apparatus of claim 1, further comprising a microcontroller configured to store a digitized correlated color temperature based on the level of the light-emitting signal received from the single control device (CCT) vs. current curve, the digitized CCT vs. current curve is used to provide an input for setting the color temperature of the LED multicolor array. The dimming and toning circuit apparatus of claim 1, wherein the single control device includes a resistive voltage divider. A dimming and toning circuit system comprising: a light emitting diode (LED) multicolor array including at least one desaturated red LED, at least one desaturated green LED and at least one desaturated blue LED; and a mixed a driver circuit coupled to the LED multicolor array, the hybrid driver circuit further coupled to a single control device and configured to receive a signal from the single control device indicating one of the desired luminous fluxes of the LED multicolor array level, the hybrid drive circuit is further configured to supply a pulse width modulated (PWM) time-division signal to selected ones of the LED multicolor array Alternatively, the hybrid drive circuit includes: an arithmetic device configured to determine an amount of current for supplying to the LED multicolor array based on the desired level of luminous flux, the arithmetic device further enabling the LED multicolor array A color temperature is related to the desired level of luminous flux; an analog shunt circuit for generating current for at least two LED current drive sources, the analog shunt circuit further comprising a resistive voltage divider circuit, the resistive voltage divider a multiplexer circuit configured to generate an amplified voltage signal; and a multiplexer array having coupled between the analog shunt circuit and the LED multicolor array and configured to drive current from the at least two LED currents At least one of the sources is periodically provided to a plurality of switching devices for at least one color of the LED multicolor array for a predetermined amount of time. The dimming and toning circuit system of claim 15, wherein the computing device is a microcontroller for mapping a received light signal level from the single control device to a correlated color temperature (CCT) to provide an input to the hybrid driving circuit to set the color temperature of the LED multi-color array. The dimming and tinting circuitry of claim 15, wherein the computing device is a microcontroller configured to store a digitized light signal level based on a received light from the single control device A correlated color temperature (CCT) vs. current curve, the digitized CCT vs. current curve is used to provide an input to the hybrid driver circuit to set the color temperature of the LED multicolor array. A method for operating a circuit comprising: Determining and supplying a set voltage as an input voltage of a voltage controlled current source; amplifying the set voltage using a resistive voltage divider circuit; determining a desired luminous flux level of a light emitting diode (LED) multicolor array; making The luminous flux level is associated with a color temperature of the LED multicolor array; an input current is divided into a first current and a second current; and a determination based on the color temperature: substantially during a first portion of a time period Simultaneously supply the first current to the first one of the three colors of the LED multicolor array and supply the second current to the second one of the three colors of the LED multicolor array; during the period of time The first current is supplied to the second of the three colors of the LED multi-color array and the second current is supplied to a third of the three colors of the LED multi-color array at substantially the same time for a second partial period and the first current is supplied to the first of the three colors of the LED multi-color array and the second current is supplied to the LED multi-color array substantially simultaneously during a third portion of the time period the third of the three colors. The method of claim 18, wherein the supply of the first current to the different even electrons of the LED multicolor array and the supply of the second current to the different even electrons of the LED multicolor array use pulse width modulation (PWM). ) time truncation occurs. The method of claim 19, wherein the PWM is substantially between a combination of the first one of the LED multicolor array, the second one of the LED multicolor array, and the third one of the LED multicolor array equal.

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